adding new attribute lock (#8)

app/config/config.go

@@ -20,6 +20,7 @@ type (
 		port          string
 		logsLevel     logrus.Level
 		logsFormatter logrus.Formatter
+		lock          bool
 		// commands associates a file extension with a Command instance.
 		// Particular case: ".pdf" extension is used for the merge command.
 		commands map[string]*Command
@@ -126,6 +127,16 @@ func GetLogsFormatter() logrus.Formatter {
 	return config.logsFormatter
 }
 
+// WithLock sets the lock strategy.
+func WithLock(lock bool) {
+	config.lock = lock
+}
+
+// HasLock returns the current lock strategy.
+func HasLock() bool {
+	return config.lock
+}
+
 type interpreterEmptyError struct {
 	command string
 }